1. Field of the Invention
This present invention relates to a display and a method for making the same, and in particular relates to a high contrast plasma display panel (PDP) and a method for making the same.
2. Description of the Prior Art
PDP uses the UV light emitted by a gas arc to excite red, green and blue phosphorous materials and generate visible light when the excited phosphorous materials return to ground state. FIG. 1A is a schematic view of the traditional PDP with electrodes, and FIG. 1B illustrates the cross-sectional view of a discharge cell of the PDP shown in FIG. 1A. As shown in FIGS. 1A and 1B, the electrodes are arrayed on a matrix consisting of vertical and horizontal stripes set on the glass substrates 1 and 2. One set of the electrodes is the address electrode 3 for the display data to write therein. Another set of the electrodes is the display electrodes 4, which is used to discharge and display. Between the display electrodes is discharge region. The region which is not covered by the discharge region is a non-discharge region. The address electrodes 3 are separated by ribs 5, and the red, green, blue phosphorous materials are coated on the glass substrate 1 to cover the address electrodes 3. The display panel is formed by joining the rear glass substrate 1 with the front glass substrate 2, and the space between the glass substrates 1 and 2 are filled with a mixing gas consisting of Ne and Ar. Each intersection of an address electrode 3 and a pair of display electrodes 4 is a discharge cell. The data written into the address electrode 3 are transformed and transferred to the display panel by discharging between the display electrodes 4. By controlling the discharge intensity of the display electrodes 4, the intensity of the emission light can be controlled and the display panel can show true color symbols, drawings and images.
The brightness and the contrast are both important properties for PDP. The definition of contrast is the ratio of the brightness level to the darkness level. As shown in FIG. 2, during operation, the PDP has a little background radiation even in full dark state. Therefore, the definition of contrast in a dark room (dark-room contrast) is the ratio of intensity of display light (Ld) over the intensity of background radiation (Lb):
Dark-room contrast=Ld/Lb
Next, consider a light environment (such as indoor illumination). Let the intensity of incident light be Lin, and the reflection coefficient of the glass substrate be xcex1. Let the the intensity of reflecting light be Lref, then Lref=xcex1Lin. The contrast in a light room (light-room contrast) is amended as the following formula:
Light-room contrast=(Ld+Lref)/(Lb+Lref)
Therefore, decreasing the intensity of the reflecting light is necessary to enhance light-room contrast.
To reduce the intensity of reflection and improve the contrast in a light room, a non-transparent black matrix (BM) is introduced to the front panel of the PDP to cover the non-discharge region of PDP.
FIGS. 3Axcx9c3G are cross-sectional views showing one process in the prior art for improving the light-room contrast by introducing black matrices onto the front panel of the PDP. In this example, black matrices are introduced into to the front panel of the PDP to improve the light-room contrast.
As shown in FIG. 3A, a glass substrate 10 is provided first. Then, transparent electrodes 12 are formed on the discharge region of the glass substrate 10 as shown in FIG. 3B. The transparent electrodes 12 usually consist of indium tin oxide (ITO). Then, display electrodes 14 are formed on top of the transparent electrode 12 as shown in FIG. 3C. The display electrodes usually consist of Cr/Cu/Cr or Cr/Al/Cr. A planarized dielectric layer 16 is deposited as shown in FIG. 3D. Then, black matrices 18 are formed on top of the dielectric layer 16 in areas corresponding to non-discharge region of PDP as shown in FIG. 3E. The black matrices 18 usually consist of black low melting-point glass. Then, a sealing frit 20 is formed on top of the dielectric layer 16 in the peripheral PDP. For illustration purpose, the sealing frit is shown next to the black matrix in FIG. 3F. Afterwards, a MgO layer 22 is formed as shown in FIG. 3G.
FIGS. 4Axcx9c4F are cross-sectional views showing another process for improving the light-room contrast by introducing a black matrix onto the front panel of the PDP.
As shown in FIG. 4A, a glass substrate 30 is provided first. Then, transparent electrodes 32 are formed on the discharge region of the glass substrate 30 as shown in FIG. 4B. The transparent electrodes 32 usually consist of indium tin oxide (ITO). Then, display electrodes 34 are formed on top of the transparent electrodes 32, and black matrices 36 are formed on the non-discharge region of the PDP as shown in FIG. 4C. Then, a planarized dielectric layer 38 is deposited as shown in FIG. 4D. Then, a sealing frit 40 is formed on top of the dielectric layer 38 in the peripheral PDP as shown in FIG. 4E.
Afterwards, a MgO layer 42 is formed on the exposed dielectric layer 38 as shown in FIG. 4F.
Similarly, FIGS. 5Axcx9c5F shows another example, wherein black matrices are introduced into to the front panel of PDP to improve the light-room contrast.
As shown in FIG. 5A, a glass substrate 50 is provided first. Then, transparent electrodes 52 are formed on the discharge region of the glass substrate 50 as shown in FIG. 5B. The transparent electrodes 52 usually consist of indium tin oxide (ITO). Then, display electrodes 54 are formed on top of the transparent electrodes 52, as shown in FIG. 5C. The display electrodes usually consist of Cr/Cu/Cr or Cr/Al/Cr. Then, a planarized dielectric layer 56 is deposited as shown in FIG. 5D. Black matrices 58 are formed on top of the dielectric layer 56 which corresponds to non-discharge region of PDP as shown in FIG. 5E, wherein the black matrices 58 usually consists of black low melting-point glass. Then, another dielectric layer 60 is deposited as shown in FIG. 5F. Then, a sealing frit 62 is formed on top of the dielectric layer 60 in the peripheral PDP as shown in FIG. 5G. Afterwards, a MgO layer 64 is formed on the exposed dielectric layer 60 as shown in FIG. 5H.
In the above-mentioned examples, the surface reflectance of the black matrices (18, 36, 58) consisting of either Cr/Cu/Cr or Cr/Al/Cr may reach as high as 60%.
One object of this present invention is to provide a high contrast PDP and a method for making the same to reduce the surface reflectance of the black masks, thus the intensity of the reflection can be reduced. Consequently, the light-room contrast is improved.
Another object of this invention is to provide a high contrast PDP and a method for making the same, which is characterized by that shielding masks formed of black matrix material below the display electrodes. Compared with the traditional PDP, the area covered by the black matrix material within this present PDP is increased, thereby the reflection intensity of PDP is reduced.
Another object of this invention is to provide a high contrast PDP, and a method for making the same. The reflection intensity can be reduced and the light-room contrast can be improved without extra processes or cost.